Settings where ecstasy is offered in pubs (7)
I believe the answer is:
locales
'settings' is the definition.
(locale means a setting or place)
'ecstasy is offered in pubs' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'is offered in' is an insertion indicator.
'pubs' becomes 'locals'.
'e' placed into 'locals' is 'LOCALES'.
'where' is the link.
(Other definitions for locales that I've seen before include "scenes" , "Spots" .)